1. Technical Field of the Invention
The present invention relates to a phased array antenna including a plurality of antenna elements and its phase calibration method for calibrating a phase of each antenna element.
2. Related Art
A phased array antenna including a plurality of antenna elements is needed to calibrate a phase of each antenna element in such a manner that radio waves outputted by the antenna elements have the same phase under a predetermined set of conditions.
In the related art, a technique is known to, upon a calibration of a phase of the plurality of antenna elements, (i) change a phase of only one arbitrary antenna element under condition that radio waves with a predetermined power is radiated, (ii) monitor a resultant change in a radiated power of all of the plurality of antenna elements at a receiver located at a front plane side of a radio wave radiation plane to obtain a phase value of the one arbitrary antenna element, (iii) perform the above steps (i) and (ii) for all antenna elements to obtain phase values of all antenna elements, and (iv) calibrate a phase of each antenna elements based on these phase values (see WO2004/013644 A1).
However, in the case where only one antenna elements is changed, a radiated power capable of being received at the receiver is low. This makes it difficult to precisely obtain a correlation between the resultant change in this one antenna element and the radiated power. Accordingly, in the case where a change in the radiated power of all antenna elements is measured, the phase of the one antenna element cannot be precisely obtained, and then a calibration of antenna elements cannot be accurately performed.